To ask if anyone knows what a "funny knocker" is?

[Monsterpage]

My 4 year old has on a number of occasions said "I"ll get you with my funny knocker". This is normally followed by him touching us on the arm or chest.
He goes to pre-school so I assume he has picked it up there. I've tried googling it to see if it features in a story but quite frankly it has brought up a raft of slightly dodgy looking websites so I've given up.
Anyone else heard it??

[Imaginesthat]

Funny bone ?

[semanwen]

A version of the song knicky ,knacky, knocky noo?

[NancyCarolinesTorch]

Bommy knocker? It's from a kids book- I can't remember what it's called but I believe the main character (a rabbit??) uses it to bop things on the head (gnomes??)